دانلود رایگان مقاله تاثیر ساختار سلسله مراتب بر خواص توزیع آلومینیوم نانوکامپوزیت اکسید / پلی اتیلن

Abstract

In the recent decades, the phenomena of space charge accumulation in the high voltage direct current (HVDC) insulation have attracted more and more attention. In this paper, the gradient-distribution multi-layered Al2O3/low density polyethylene (LDPE) nanocomposites were prepared via layer-by-layer melting blending and hot pressing method. Morphologies and electrical properties of these gradient-distribution structured composites were discussed. Results showed that this unique structure could largely enhance the breakdown strength of LDPE. The breakdown strength of the LDPE nanocomposites varied with nano-Al2O3 concentrations, and it could reach to 200 kV/mm for the LDPE nanocomposites. Besides, space charge of the LDPE nanocomposites was measured by pulsed electro-acoustic (PEA) method. The charge profiles indicated that space charge suppression of the gradient-distribution multi-layered composites was better than that of the monolayer ones with general mean-distribution structure. Their excellent insulating properties were attributed to the trap which exists in the surface, and that could well inhibit the charge injecting into the materials.

4. Conclusions

The gradient-distribution Al2O3/LDPE nanocomposites with multi-layered structure were prepared in this paper. Compared with the general mean-distribution structured monolayer composites, these composites with unique morphology have excellent electrical properties as follows. For the gradient-distribution structured LDPE nanocomposites, there was no clear interface between the adjacent layers, though they were prepared through two-time hot pressing progress. This continuous morphology can well avoid the air layer. Meanwhile, the polymer molecules in thermal motion during the hot pressing process, makes the whole molecule rearrangement. This rearrangement of molecule chains contributes to its forming stable conformation, which has the minimum molecular force. Space charge amount of the gradientdistribution structured LDPE nanocomposites is less than that of the mean-distribution structured ones as the trap near the composites surface can capture the injected charges. The captured charges can distort the electric field in the vicinity of the interface, which will decrease the charge injection. Thus, the space charges can be suppressed. Meanwhile, the nano-Al2O3 tends to distribute in the interface between the neighbouring layers. It suggests that the carriers prefer to conduct through this interaction zone, then causing the space charge suppression.